This background information and document(s) mentioned below is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention, and in particular allowing the reader to understand advantages of the invention over methods known to the inventor, but not necessarily public, methods. No admission is necessarily indented, nor should be construed, that CA2,820,742 or figures shown as FIGS. 1-3 herein constitute legally citable prior art against the present invention, and priority is claimed therefrom.
Canadian Patent Application CA 2,820,742 filed Jul. 4, 2013 entitled “Improved Hydrocarbon Recovery Process Exploiting Multiple Induced Fractures”, which is commonly assigned with this application, discloses in one aspect thereof a method of providing lateral drive of fluids in a reservoir by injecting fluids into a first set of vertical fractures which extend radially outwardly from a first horizontal well, and producing reservoir fluids from second set of vertical fractures which extend upwardly and radially outwardly from a second horizontal well substantially parallel to the first horizontal well, and which second set of vertical fractures are preferably laterally offset from said first set of vertical fractures, as set out in FIG. 1 of such patent application.
Notably, however, the cost of both drilling and fracturing a pair of (i.e. two) horizontal wells is obviously twice the capital cost if only a single fractured horizontal well was only needed to be used to laterally drive such oil from a region of a reservoir being developed.
CA 2,820,742 further discloses, however, a process for the enhanced recovery of oil from a subterranean reservoir using a lateral drive, and using only a single horizontal production well, having a single set of vertical fractures extending radially outwardly therefrom. In such embodiment an enhanced oil recovery fluid is injected into alternate fractures within the reservoir, and oil which drains downwardly into the horizontal well via the remaining fractures is collected in such horizontal well and thereafter produced to surface, as is shown by the method as depicted in FIGS. 4a-4c and 5a-5c of CA 2,820,742.
Disadvantageously, however, as more fully explained herein, the single horizontal well method as taught in CA 2,820,742 when applied to an open horizontal wellbore (as opposed to a cased horizontal wellbore) and particularly when using gas as the enhanced oil recovery fluid which is injected, will suffer in certain conditions from such injected fluid (gas) bypassing the single packer by travelling through the reservoir immediately adjacent the horizontal wellbore, and thence back into the wellbore thereby bypassing the formation, thereby greatly reducing or eliminating the effectiveness of the gas to drive oil to adjacent hydraulic fractures in the formation, where it can drain down and subsequently be collected.
Accordingly, a real need exists for an effective fluid drive method for sweeping petroleum from an underground reservoir which utilizes a single wellbore and which thus saves capital costs in otherwise having to drill and fracture a second wellbore, but further avoids the problems in the case where the injected fluid is a gas, of bypass as discussed above.